Accelerator composition for elastomers

ABSTRACT

The invention relates to an accelerator agent of a novel blend of aldehyde-amine condensation product and aliphatic amines for diaminic, metal oxide, sulfur, and triazine crosslinkable elastomers.

BACKGROUND OF THE INVENTION

The invention relates to an accelerator agent comprising a novel blendof aldehyde-amine condensation product and aliphatic amines, for usewith diaminic, metal oxide, sulfur, and triazine crosslinkableelastomers, in particular, ethylene acrylate elastomers (AEM) andpolyacrylate elastomers (ACM), polyisoprene (IR), styrene butadiene(SBR), acrylonitrile butadiene (NBR), ethylene-propylene dieneterpolymers (EPDM), isobutylene-co-isoprene (IIR), chlorinatedisobutylene-co-isoprene (CIIR), and brominated isobutylene-co-isoprene(BIIR).

Diaminically crosslinkable ethylene acrylate elastomers (AEM) andpolyacrylate elastomers (ACM) are relatively inexpensive elastomericmaterials which are of interest in the area of seals, particularly thoseused in various elements of vehicle engines. AEM elastomers areavailable, for example, from DuPont under the trade name Vamac®, whileACM elastomers are available from Zeon Chemicals, for example, under thetrade names Nipol® and HyTemp®.

Those AEM and ACM elastomers which are accessible to diaminiccrosslinking comprise so-called cure site monomer units whose content inthe elastomer is normally approximately 1 to approximately 5 phr.Conventionally, diaminically crosslinkable AEM and ACM elastomers arecrosslinked with crosslinking agents such as, for example, hexamethylenediamine carbamate, N,N-dicinnamylide diamine carbamate,4,4-diaminodicyclohexylmethane, m-xylene diamine,4,4-diaminodiphenylmethane, 4,4-diaminodiphenyl ether and2,2-bis[4-(4-amino-phenoxy)phenyl]propane, which can be usedindividually or in mixtures. Other suitable diamine crosslinking agentsbelong to the group of hexamethylene diamines.

US 2009/0270549 teaches a crosslinking agent for diaminicallycrosslinkable ethylene acrylate (AEM) and polyacrylate (ACM) elastomers,comprising a diamine crosslinker, an accelerator selected from1,8-diazabicyclo-5,4,0-undec-7-ene (DBU), derivatives and salts thereof,and a moderator of the pyrrolidone type. The reference notes that whileDBU, a tertiary amine, was a known accelerator, it was not possible touse with these AEM and ACM elastomers as it resulted in inferiorcompression set at elevated temperatures. The reference teaches that theproblem is overcome by combining DBU with a moderator.

Polychloroprene (CR) and natural rubber (NR) elastomers are relativelyinexpensive elastomeric materials which are used in many broad rangerubber applications. CR elastomers are available, for example, fromDuPont under the name Neoprene, while NR elastomers are widely availableunder many technical specified descriptions of natural rubber.

General purpose CR is used in molded and extruded goods, hoses, belts,wire and cables, heels and soles of shoes, coated fabrics, and gaskets.Most natural rubber is used in tires and automotive products. Othermajor applications of NR are industrial and engineering goods, footwearand adhesives.

CR and NR use differing crosslinking systems for their differentpolymeric chemical makeup. CR uses metal oxides as a curative while NRuses sulfur as its curative. Both crosslinking systems are used togetherwith an accelerator, of which can be from a wide variety of chemicalgroups.

Polyepichlorohydrin is a triazine crosslinkable elastomer group, ofwhich epichlorohydrin polymer (CO), copolymer of epichlorohydrin (ECO),and terpolymer of epichlorohydrin (GECO) are examples.Polyepichlorohydrin elastomers have a balance of properties that make ituseful in automotive seals and hoses, and are available from ZeonChemicals, for example, under the trade name Hydrin®.

Triazine crosslinking systems can be used with a variety of acceleratorsand retarders to make the cure systems widely adjustable.

These crosslinking systems are used together with an accelerator, whichis preferably taken from substances of the guanidine group, to which, inparticular, the accelerators OTBG, DOTG, DPG and/or biguanidine belong.However, due to possible toxicological problems, it is likely that thesesystems, particularly DOTG, will be phased out under regulatoryrequirements.

SUMMARY OF THE INVENTION

The present invention relates to an accelerator agent for crosslinkableelastomers. In particular, the invention relates to a novel blend of analdehyde-amine condensation product and an aliphatic amine. Thealdehyde-amine condensation products may be of the type represented, forexample, by 3,5-diethyl-1,2-dihyrdro-1-phenyl-2-propylpyridine (“PDHP”),a condensation product of butyraldehyde and aniline (“B-A rxn”), and acondensation product of butryaldehyde and butylamine.

The aliphatic amine is a mixture of high molecular weight fatty aminesderived from natural sources (dialkyl secondary amines), such asdicocoalklyamine (“DCAA”), bis(hydrogenated tallow alkyl)amine (“BHTAA”)and 1-Octadecanamine, N-octadecyl-amine.

It has been surprisingly found that a blend of aldehyde-aminecondensation product and aliphatic amine can successfully be substitutedfor DOTG as an accelerator in the manufacture of elastomeric compounds.This novel accelerator blend is able to achieve outstanding results indiaminically crosslinkable AEM and ACM without the need of a pyrrolidonemoderator, and as a direct replacement in metal oxide, sulfur, andtriazine crosslinkable elastomers.

The accelerator blend may be present in the elastomer composition at upto 1-10 phr, preferably 0.2-4 phr. The blend itself may consist of thealiphatic amine and aldehyde-amine condensation product in a ratio byweight of about 1:10 to 10:1, preferably from 2:1 to 6:1. The inventionresides in both the accelerator blend per se, and an elastomercomposition comprising the blend.

DETAILED DESCRIPTION OF THE INVENTION

Applicants studied the effectiveness of substitutions for DOTG in AEM,ACM, CR, NR and ECO elastomeric compounds. The purpose of this inventionwas to provide a replacement for DOTG in cure systems for elastomerswhich retains similar physical properties to the DOTG containingcompound. This invention uses the blend of aliphatic amines and analdehyde-amine condensation product to replace DOTG in elastomers. Thiscombination gives similar physical properties (+/−20%) to DOTG whilemaintaining similar processing characteristics of the rubber compoundand retained properties after heat aging.

The physical properties of importance are:

-   -   Compression Set    -   Aged Elongation    -   Aged Tensile Strength        To show accelerator effectiveness, the following rheology        properties were monitored:    -   Cure State by Maximum Torque, MH    -   Cure time, t′90

In order to demonstrate the synergistic effect, we examined the use ofeach component separately and their resultant property trends. Testingwas first done in AEM to develop an acceptable accelerator and thenconfirmed its performance in ACM, CR, NR, and ECO. This inventionrelates to the use of this novel accelerator blend in diaminic, metaloxide, sulfur, and triazine crosslinkable elastomers.

The master batch for the AEM elastomer is set forth in Table 1 below.

TABLE 1 Control AEM recipe with generic chemical and use descriptions,and control testing conditions: Ingredients phr AEM G (ethylene acrylicelastomer) 100.0 N774 Carbon Black (filler) 65.0 Stearic Acid (releaseagent) 1.5 Octadecylamine (release agent) 0.5 Dicumyl diphenylamine(antioxidant) 2.0 Polyoxyethylene octadecyl ether phosphate 1.0 (releaseagent) HDMC (crosslinking agent) 1.5 DOTG (accelerator) 4.0 ASTM D5289 -Moving Die Rheometer @ 177° C., 0.5° Arc Slabs Cured 10 min. @ 177° C.and Postcured 4 hrs. @ 175° C. ASTM D412, Method A, Die D - StressStrain Tests ASTM D573 - Aging 168 hrs. @ 177° C. ASTM D395, Method B,Plied Disks - Compression Set After 168 hrs. @ 177° C.

Applicants studied the effectiveness of substitutions for DOTG in AEMelastomers, particularly3,5-diethyl-1,2-dihyrdro-1-phenyl-2-propylpyridine (PDHP),bis(hydrogenated tallow alkyl)amines (BHTAA), and finally blend of thetwo components. This invention uses the blend of aliphatic amines and analdehyde-amine condensation product to replace DOTG.

Use of the BHTAA and PDHP alone is shown against the combination of thetwo components in Table 2. The superior results from the combination ofthe two products show the synergistic effect of the blend when comparedto each of the product's physical property trends alone.

The optimal blend ratio of 6:1 BHTAA:PDHP was then tested to show theworking ranges of this combination. The most preferred phr level is anequivalent usage to the DOTG at 4 phr. The summary data in Table 2 showsthat up to a 10 phr level gives an effective working range of thiscombination. The preferred usage level is 0.2-4 phr, and 10 phr is theouter usage level.

The ratio of the blending was tested to show the working range of thiscombination. The summary data in Table 3 proves that even the far rangesof a blend at a 1:10 and a 10:1 ratio gives improved performance overthe same usage level of the products alone, with the most preferredblend ratio being a 6:1 BHTAA:PDHP level.

TABLE 2 R-2022 BHTAA/ BHTAA/ DOTG BHTAA PDHP PDHP 6:1 PDHP 6:1 (4 phr)(4 phr) (4 phr) (4 phr) (10 phr) CSet, % 35.4 38.1 41.1 35.6 37.4 Aged176 219 177 216 182 Elongation, % Aged Tensile 12.29 13.60 13.67 14.5512.49 Strength, MPa MH, dN-m 14.88 12.39 12.70 13.56 12.29 t′90, min.10.84 12.98 6.32 11.51 10.53

TABLE 3 R-2012 BHTAA/ BHTAA/ DOTG PDHP 1:10 PDHP 10:1 (4 phr) (4 phr) (4phr) CSet, % 34.1 39.3 35.1 Aged Elongation, % 189 170 192 Aged Tensile13.39 12.06 13.13 Strength, MPa MH, dN-m 13.60 11.74 12.18 t′90, min.7.68 6.24 8.29

Finally, other types of starting materials were tested to show the novelblend of aldehyde-amine condensation product and aliphatic amines worksin addition to the specific components studied.

The aliphatic amine dicocoalklyamine (“DCAA”) was tested alone and incombination with PDHP to show the combination of these two also canreplace DOTG (Table 4). The optimal blend ratio of 6:1 was tested at ahigh and low level range of 2 and 10 phr. The optimal phr level wastested with the far ratio range of 10:1 DCAA:PDHP.

TABLE 4 R-2024 DCAA/ DCAA/ DCAA/ DOTG DCAA PDHP 6:1 PDHP 6:1 PDHP 10:1(4 phr) (4 phr) (2 phr) (10 phr) (4 phr) CSet, % 35.6 35.4 34.9 38.833.8 Aged 190 254 243 191 228 Elongation, % Aged Tensile 13.23 15.4314.97 12.09 14.27 Strength, MPa MH, dN-m 15.23 13.20 13.75 12.09 13.63t′90, min. 8.69 12.57 11.96 11.11 11.66

Next, the aldehyde-amine condensation product butyraldehyde and aniline(“B-A rxn”) was tested alone and in combination with BHTAA to show itscombination can replace DOTG (Table 5). The optimal blend ratio of 6:1was tested at a phr level range of 2 and 8 phr. The optimal phr levelwas tested at an additional ratio range of 3:1 BHTAA:B-A rxn.

TABLE 5 R-2038 BHTAA/ BHTAA/ BHTAA/ DOTG B-A rxn B-A rxn B-A rxn B-A rxn(4 phr) (4 phr) 6:1 (2 phr) 6:1 (8 phr) 3:1 (4 phr) CSet, % 36.6 45.440.6 39.3 37.9 Aged 237 186 234 173 219 Elongation, % Aged Tensile 17.7915.02 17.03 13.72 16.63 Strength, MPa MH, dN-m 14.54 13.17 12.38 11.8612.70 t′90, min. 12.18 9.72 13.73 13.04 12.45

The various blend ratios and phr level uses confirm the working rangesof the aldehyde-amine condensation product and aliphatic aminescombination while using other starting materials.

Additional testing was done in the ACM polyacrylate elastomer to showthat these combinations also provide similar physical properties to DOTGin that acrylic elastomer.

The master batch for the ACM elastomer is set forth in Table 6 below.

TABLE 6 Control ACM recipe with generic chemical and use descriptions,and control testing conditions: Ingredients phr ACM 212HR (polyacrylateelastomer) 100.0 N550 Carbon Black (filler) 60.0 Stearic Acid (releaseagent) 1.0 Dicumyl diphenylamine (antioxidant) 2.0 Release package 2.0HDMC (crosslinking agent) 0.6 DOTG (accelerator) 2.0 ASTM D5289 - MovingDie Rheometer @ 190° C., 0.5° Arc Slabs Cured 6 min. @ 190° C. andPostcured 4 hrs. @ 177° C. ASTM D412, Method A, Die D - Stress StrainTests ASTM D573 - Aging 168 hrs. @ 190° C. ASTM D395, Method B, PliedDisks - Compression Set After 24 hrs. @ 175° C.

The summary data in Table 7 proves that the far ranges of a blend at a1:10 and a 10:1 ratio gives improved performance over the same usagelevel of the products alone, with the most preferred blend ratio being a6:1 BHTAA:PDHP level. In this elastomer, 2 phr is the optimal use leveland Table 7 also shows the preferred ratio blend also working at ahigher level of 4 phr. This data proves the combination ofaldehyde-amine condensation product and aliphatic amines can provide thephysical results to replace DOTG in ACM as well as in AEM.

TABLE 7 R-2035 BHTAA/PDHP BHTAA/PDHP BHTAA/PDHP BHTAA/PDHP DOTG BHTAAPDHP 10:1 1:10 6:1 6:1 (2 phr) (2 phr) (2 phr) (2 phr) (2 phr) (2 phr)(4 phr) CSet, % 16.2 21.1 21.8 18.3 20.4 17.5 17.2 Aged Elongation, %192 197 137 173 129 193 155 Aged Tensile 8.20 7.54 8.67 7.42 8.61 8.108.49 Strength, MPa MH, dN-m 9.55 7.77 9.89 7.94 10.13 8.29 8.61 t′90,min. 7.55 10.30 5.11 10.38 5.47 10.31 9.70

This invention was next tested in other crosslinkable elastomers systemsto show that an accelerator agent of a novel blend of aldehyde-aminecondensation product and aliphatic amines also replaces DOTG for metaloxide, sulfur, and triazine crosslinkable elastomers.

The master batch for the CR, NR, ECO elastomers is set forth in Tables8-10 respectively, below.

TABLE 8 Control CR recipe with generic chemical and use descriptions,and control testing conditions: Ingredients phr CR W (polychloropreneelastomer) 100.0 N774 Carbon Black (filler) 60.0 Stearic Acid (releaseagent) 0.5 Naphthenic oil (process oil) 5.0 Plasticizer 5.0 Octylateddiphenylamines (antioxidant) 2.0 Magnesium oxide (curative) 4.0 ZincOxide (crosslinking agent) 5.0 Sulfur (cure modifier) 1.0 Tetramethylthiuram monosulfide 1.0 (accelerator) DOTG (accelerator) 1.0 ASTMD5289 - Moving Die Rheometer @ 160° C., 0.5° Arc Slabs Cured t′90 + 2min. @ 160° C., Buttons Cured t′90 + 12.5 min@ 160° C. ASTM D412, MethodA, Die D - Stress Strain Tests ASTM D573 - Aging 336 hrs. @ 100° C. ASTMD395, Method B - Compression Set After 70 hrs. @ 121° C.

TABLE 9 Control NR recipe with generic chemical and use descriptions,and control testing conditions: Ingredients phr NR L (natural rubberelastomer) 100.0 N990 Carbon Black (filler) 35.0 N330 Carbon Black(filler) 30.0 Stearic Acid (release agent) 2.0 Zinc Oxide (cureactivator) 5.0 Plasticizer 2.0 Process Aid 2.0 Octylated diphenylamines(antioxidant) 1.5 Sulfur (crosslinking agent) 2.5 Benzothiazyl disulfide(accelerator) 0.5 DOTG (accelerator) 0.5 ASTM D5289 - Moving DieRheometer @ 160° C., 0.5° Arc Slabs Cured t′90 + 2 min. @ 160° C.,Buttons Cured t′90 + 12.5 min@ 160° C. ASTM D412, Method A, Die D -Stress Strain Tests ASTM D573 - Aging 168 hrs. @ 100° C. ASTM D395,Method B - Compression Set After 22 hrs. @ 100° C.

TABLE 10 Control ECO recipe with generic chemical and use descriptions,and control testing conditions: Ingredients phr ECO C2000(epichlorohydrin elastomer) 100.0 N330 Carbon Black (filler) 50.0Stearic Acid (release agent) 1.0 Magnesium Oxide (cure activator) 3.0Calcium Carbonate (filler) 5.0 Nickel dibutyldithiocarbamate 1.0(antioxidant) 2,4,6 Trimercapto-s-triazine 1.0 (crosslinking agent) DOTG(accelerator) 0.2 ASTM D5289 - Moving Die Rheometer @ 200° C., 0.5° ArcSlabs Cured t′90 + 2 min. @ 200° C., Buttons Cured t′90 + 12.5 min@ 200°C. ASTM D412, Method A, Die D - Stress Strain Tests ASTM D573 - Aging168 hrs. @ 125° C. ASTM D395, Method B - Compression Set After 22 hrs. @125° C.

The summary data in Table 11 shows that the blend gives improvedperformance over the same usage level of the products alone in the metaloxide crosslinkable CR elastomer. The blend ratio was tested at a 1:1and a 6:1 BHTAA:PDHP level and at a 1 phr and 2 phr usage level. Thisdata proves the combination of aldehyde-amine condensation product andaliphatic amines can provide the physical results to replace DOTG inmetal oxide crosslinkable elastomers.

TABLE 11 R-2039 BHTAA/PDHP BHTAA/PDHP BHTAA/PDHP BHTAA/PDHP DOTG BHTAAPDHP 1:1 1:1 6:1 6:1 (1 phr) (1 phr) (1 phr) (1 phr) (2 phr) (1 phr) (2phr) CSet, % 58.6 64.8 55.6 58.8 53.0 61.0 55.1 Aged Elongation, % 179196 185 180 183 194 188 Aged Tensile 18.74 18.43 18.92 19.39 19.10 18.7818.15 Strength, MPa MH, dN-m 19.70 18.19 21.08 19.50 20.02 18.99 19.66t′90, min. 30.28 39.79 16.65 27.28 14.01 32.86 25.36

The summary data in Table 12 shows that the blend gives improvedperformance over the same usage level of the products alone in thesulfur crosslinkable NR elastomer. The blend ratio was tested at a 1:1and a 6:1 BHTAA:PDHP level and at a 1 phr and 2 phr usage level. Thisdata proves the combination of aldehyde-amine condensation product andaliphatic amines can provide the physical results to replace DOTG insulfur crosslinkable elastomers.

TABLE 12 R-2040 BHTAA/PDHP BHTAA/PDHP BHTAA/PDHP BHTAA/PDHP DOTG BHTAAPDHP 1:1 1:1 6:1 6:1 (1 phr) (1 phr) (1 phr) (1 phr) (2 phr) (1 phr) (2phr) CSet, % 58.4 54.5 63.5 58.5 62.8 54.7 60.2 Aged Elongation, % 114136 132 124 132 120 118 Aged Tensile 6.45 7.03 7.60 7.37 6.94 7.09 7.18Strength, MPa MH, dN-m 19.23 14.42 22.78 20.57 21.82 15.91 18.15 t′90,min. 3.92 5.47 2.59 3.17 2.45 4.52 3.54

The summary data in Table 13 shows that the blend gives improvedperformance over the same usage level of the products alone in thetriazine crosslinkable ECO elastomer. The optimal blend ratio of 6:1BHTAA:PDHP level was tested against both DOTG and DPG guanidines. Thisdata proves the combination of aldehyde-amine condensation product andaliphatic amines can provide the physical results to replace guanidinesin triazine crosslinkable elastomers.

TABLE 13 R-2049 BHTAA/ DOTG DPG PDHP 6:1 (0.2 phr) (0.2 phr) (0.2 phr)CSet, % 21.8 21.1 20.5 Aged Elongation, % 267 261 286 Aged Tensile 17.5117.57 17.55 Strength, MPa MH, dN-m 25.77 26.37 24.38 t′90, min. 3.693.50 4.90

This invention of blend of aldehyde-amine condensation product andaliphatic amines can successfully be substituted for DOTG as anaccelerator in the manufacture of diaminic, metal oxide, sulfur, andtriazine crosslinkable elastomeric compounds

1. A crosslinking accelerating agent for crosslinkable elastomers, theagent comprising: an aldehyde-amine condensation product and analiphatic amine at a weight ratio of about 1:10 to about 10:1.
 2. Theagent of claim 1, wherein the ratio is about 6:1.
 3. The agent of claim1, wherein the aliphatic amine is a mixture of high molecular weightfatty amines.
 4. The agent of claim 3, wherein the aliphatic amine ischosen from the group consisting of bis(hydrogenated tallow alkyl)amine,dicocoalklyamine and 1-Octadecanamine, N-octadecylamine.
 5. The agent ofclaim 4, wherein the aliphatic amine is bis(hydrogenated tallowalkyl)amine.
 6. The agent of claim 1, wherein the aldehyde-aminecondensation product is chosen from the group consisting of3,5-diethyl-1,2-dihyrdro-1-phenyl-2-propylpyridine (“PDHP”), acondensation product of butyraldehyde and aniline, and a condensationproduct of butryaldehyde and butylamine.
 7. The agent of claim 6,wherein the aldehyde-amine condensation product is PDHP.
 8. The agent ofclaim 1, wherein the aliphatic amine is bis(hydrogenated tallowalkyl)amine and the aldehyde-amine condensation product is PDHP.
 9. Theagent of claim 8, wherein the ratio of aliphatic amine to aldehyde-aminecondensation product is about 6:1.
 10. An elastomer product, comprising:A crosslinkable elastomer chosen from the group consisting of ethyleneacrylate elastomer (AEM), polyacrylate elastomer (ACM), polychloroprene(CR), natural rubber (NR), polyisoprene (IR), styrene butadiene (SBR),acrylonitrile butadiene (NBR), ethylene-propylene diene terpolymers(EPDM), isobutylene-co-isoprene (IIR), chlorinatedisobutylene-co-isoprene (CIIR), brominated isobutylene-co-isoprene(BIIR), epichlorohydrin polymer (CO), copolymer of epichlorohydrin(ECO), and terpolymer of epichlorohydrin (GECO) elastomer and acrosslinking agent present at 1-10 phr, the crosslinking agentcomprising an aliphatic amine and an aldehyde-amine condensation productat a weight ratio of 1:10 to 10:1.
 11. The product of claim 10, whereinthe crosslinking agent is present at 1-6 phr.
 12. The product of claim11, wherein the crosslinking agent is present at about 4 phr.
 13. Theproduct of claim 10, wherein the aliphatic amine is a mixture of highmolecular weight fatty amines.
 14. The product of claim 13, wherein thealiphatic amine is chosen from the group consisting of bis(hydrogenatedtallow alkyl)amine, dicocoalklyamine and 1-Octadecanamine,N-octadecylamine.
 15. The product of claim 14, wherein the aliphaticamine is bis(hydrogenated tallow alkyl)amine.
 16. The product of claim10, wherein the aldehyde-amine condensation product is chosen from thegroup 3,5-diethyl-1,2-dihyrdro-1-phenyl-2-propylpyridine (“PDHP”), acondensation product of butyraldehyde and aniline, and a condensationproduct of butryaldehyde and butylamine.
 17. The product of claim 16,wherein the aldehyde-amine condensation product is PDHP.
 18. The productof claim 10, wherein the aliphatic amine is bis(hydrogenated tallowalkyl)amine and the aldehyde-amine condensation product is PDHP.
 19. Theproduct of claim 18, wherein the ratio of aliphatic amine toaldehyde-amine condensation product is about 6:1.
 20. The product ofclaim 19, wherein the agent is present at 4 phr.